This invention relates to a data recording method and apparatus, a data record medium and a data reproducing method and apparatus applicable to prevention of copying or inhibition of unauthorized use and to a charging system.
Recently, with increased capacity and coming into widespread use of a digital record (recording, recordable or recorded) medium, increasing importance is attached to prevention of copying or inhibition of unauthorized use. That is, since digital audio data or digital video data can be duplicated free of deterioration by copying or dubbing, while computer data an be easily copied to produce the same data as the original data, unauthorized copying is made frequently.
For avoiding unauthorized copying of the digital audio or video data, there is known a standard such as a so-called serial copying management system (SCMS) or copy generation management system (CGMS). Since these systems set a copying inhibition flag on a specified portion of record data, a problem is raised that data can be extracted by dump copying which is the copying of a digital bi-level signal in its entirety.
It is also practiced to cipher the contents of a file itself in case of computer data and to permit use only by regular registered user, as disclosed in, for example, Japanese Patent laid-Open No.SHO-60-116030. This is connected to a system in which a digital record medium having the ciphered information recorded thereon is distributed as a form of information circulation and in which the user pays a fee for the information he or she needs to acquire a key to decipher the information for use. For this system, a simplified useful technique for ciphering has been a desideratum.
In view of the above-depicted status of the art, it is an object of the present invention to provide a data recording method and apparatus, a data record medium and a data reproducing method and apparatus whereby ciphering can be realized by a simplified structure, prevention of copying or unauthorized use can be achieved by a simplified configuration, deciphering is rendered difficult and relative facility or depth of ciphering can be controlled easily.
The recording method according to the present invention is characterized in that an input is ciphered in at least one of a sector forming step of dividing input digital data in terms of a pre-set data volume as a unit, a header appendage step, an error correction and decoding step, a modulation step for effecting modulation in accordance with a pre-set modulation system, or a synchronization appendage step for appendage of a synchronization pattern. A scrambling step of effecting randomizing for eliminating the same pattern may be included among the steps that can be used for ciphering.
This data recording method can be applied to a data recording apparatus.
A data reproducing method according to the present invention is characterized in that, in reproducing a data record medium recorded in the above data recording method, an input has been ciphered in a recording step corresponding to at least one of a synchronization separation step, a demodulating step, an error correction and decoding step, a sector resolving step and a header separation step, and in that the input is decoded in a reproducing step corresponding to the recording step used for ciphering. A descrambling step of descrambling for scrambling used for recording may be included among the steps that can be used for deciphering.
The data reproducing method can be applied to a data reproducing apparatus.
With the data recording method according to the present invention, the above object is accomplished by ciphering the data using the pre-set key information and by using the information written in an area different from a data recording area of the record medium as at least a portion of the key information for ciphering. This can be applied to the data recording apparatus and to a data record medium.
The data reproducing method according to the present invention is also characterized in that, in reproducing the digital signal ciphered during recording, deciphering is done using the key information at least part of which is the information written in an area different from a data recording area of the record medium.
This can be applied to a data reproducing apparatus.
The data recording method according to the present invention is also characterized by varying at least one of the initial value of the scrambling step or the generating polynomial depending on the key information for ciphering.
The data reproducing method according to the present invention is also characterized by descrambling by varying at least one of the initial value or the generating polynomial based upon the key information used for recording.
The input digital data is divided into sectors in terms of a pre-set data volume as a unit, and the resulting data is processed with header appendage, error correction and encoding, modulation by a pre-set modulation system and appendage of a synchronization pattern for recording on a record medium. By ciphering an input in at least one of the above steps, the particular step in which ciphering has been dome also becomes a key for ciphering thus raising the difficulty in deciphering.
At least a portion of the key information for ciphering is written in an area different from the recording area on the record medium. This portion of the key information is read out at the time of reproduction and used for deciphering. Since the key information is not completed with the information in the data recording area on the record medium, difficulty in deciphering is increased.
At least one of the generating polynomial or the initial value is varied depending on the key for ciphering at the time of scrambling aimed at randomization for removing the same pattern in a data string. Any conventional scrambling may be used for ciphering.